Games with more than 2 players/teams, particularly on balanced maps such as Chinese Checkers, often last a long time as no single player is willing to attack and weaken himself to hand victory to another player. Using flat rate or no spoils also increases the chances that it will become a build game.
Anyhow, here are the oldest currently running games:
Game 387875 - 3289 days
Game 578682 - 3238 rounds
I believe there was a CCU game which broke both of those records, but I don't know any other identifying characteristics of it. Perhaps somebody else could post it?
This is my longest, a feeble 355 rounds:
Game 2958057
Approaching the opposite extremity, I eliminated 29 players in only 3 rounds:
Game 6207869
Games like this are always impressive, it lasted 1 round:
Game 5919165